Pecans: Black Aphids & Mites

Reports here are that black aphids are out but numbers are not necessarily high yet.

UGA Extension Entomologist Dr. Will Hudson has this INSECT update for us:

Black Aphid damage

Black Aphids

Growers across the state are seeing an increase in black aphids. For growers with old Schley trees this has been going on for a while, but the other susceptible varieties like Sumner and Gloria Grande are experiencing a build-up now.  Remember, if you see nymph clusters you need to take steps to protect your foliage and avoid the kind of damage that can affect your crop next year.  Imidacloprid still controls black aphids pretty well, but requires the higher rate on the label (several formulations are available; the 2 lb materials need 5.6 oz/acre).  Other neonicotinyls like Belay and Assail are also effective.  If you also have yellow aphids then Carbine, or Fulfill would control both. Closer is one of the most effective options at the moment.

Mite damage on pecan leaf

Mites

We are also seeing some mite flare-ups in scattered orchards. Mites can be controlled with abamectin products (Agri-Mek, Abba Plus, etc.), Portal, Acramite, or Nexter.  The Nexter will get both aphids and mites, and may be a good choice where those pests are present and a weevil spray is needed or likely. Check labels for rates and surfactant requirements.

Insecticide Rainfast?

Dodging showers can be a challenge if you need to treat lots of acres with few sprayers, and sometimes the rain catches you or pops up right after application. If it starts to rain while you are spraying, stop the sprayer.  It will do little good to apply an insecticide (or fungicide) that will be washed off immediately.  If the rain comes after you finish, you may be okay if the spray has dried on the leaves.  A good rule of thumb is that if you get a rain within 1 hour or less of spraying and you will need to retreat.”

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Row Crop Disease Update

In cotton this week checking whiteflies, we are reaching treatable thresholds by the way… I am also seeing some target spot in RANK cotton. Also, it is very low on the plant and is not moving up. Cotton I’ve looked at is 4th and 5th week of bloom. Below is a current disease update from UGA Extension Pathologist Dr. Bob Kemerait:

Cotton

The current weather is very favorable for development of target spot and also spread of bacterial blight.  To date, bacterial blight is only a problem in susceptible varieties…The season is not over yet, and things could change.

Target Spot seen in ‘rank’, irrigated cotton, but on the very lower leaves.

TARGET SPOT:  In some, but not all, of your trials  target spot is a significant issue. From your trials, some varieties are CLEARLY for susceptible. Conditions we have now are perfect for it.  Should every grower spray every field for target spot?  NO!  But growers SHOULD BE AWARE. In one field, target spot was becoming established, and I told him I would likely treat the field with a fungicide. In another field, no target spot was found and I told him I would not treat that field.

Peanuts

We are at a critical point in the peanut season. Reports of white mold in fields are coming in every day and I am receiving some reports of leaf spot. I don’t know of any fields where leaf spot is “out of control” and only one field where white mold is “breaking loose”.  However, both diseases can be explosive given the right environment and time to become established. Growers should stay on an appropriate fungicide program for these diseases and also Rhizoctonia limb rot. Timeliness and coverage are CRITICAL.

Soybeans

Asian soybean rust has been puzzling this year. We found it in kudzu very early in the season, yet to date it remains confined to kudzu in our southern tier of counties. I still expect soybean rust to “break out” as southern corn rust has done, but I can’t understand what it is doing now. Fortunately, our Sentinel Plots are being monitored, so we can keep you up-to-date. Even though the disease has been slow to develop, I still believe that there is merit, especially in southern Georgia, to protect the soybeans during late-bloom/early pod set, especially when applying something like dimilin and boron. There are other diseases, such as frogeye leaf spot, which can be problematic and that can be managed with the same fungicides at the same time.

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Pond “UFO”?

We were looking at some pond weeds this week and saw an Unidentified “Floating” Object. Well, it wasn’t exactly floating. But it looked like Jell-O sitting on the bottom. We picked it up and set it on the ground. It’s texture was like a jellyfish. We cut it into also.

It turned out to be an invertebrate animal referred to as ‘Bryozoan colonies.’ UGA Extension Aquatic Scientist Dr. Gary Burtle says Bryozoans live in relatively clean water. Does it have any relation to fishing? Dr. Burtle says:

They may indicate that the bream population of this pond is not very abundant. Ask about fishing success and if bream are caught.  Sometimes, in a bass overcrowded pond, the bream population is so low that these invertebrates can thrive.

Bryozoan invertebrate from a pond

Bryozoan cut in half

You may have seen these before. This is one of those, ‘you learn something knew everyday.’ The Smithsonian Marine Station has more information.

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Foliage Feeding Caterpillars In Peanuts

We’ve been treating for worms in peanuts now. I’m seeing some loopers mostly. But there are reports of tobacco budworm, and I do see some TBW moths flying. We need to be scouting when we are in the field. The biggest question is our threshold.

Egg mass from armyworms (left); and ‘windowpane’ feeding (right)

Threshold

For foliage feeding caterpillars, our threshold is 4 – 8 per row foot. Remember, peanuts can tolerate a significant amount of defoliation with no impact on yield, but when we start to see ragged leaves, it becomes difficult to hold back. Our peanuts look really good thanks to timely rainfall. When peanuts are not stressed, we can go closer to 8 on the threshold.

Caterpillars feeding on blooms?

This was in issue a few years ago where UGA Extension Entomologist Dr. Mark Abney had this to say:

Bloom feeding has been observed in peanut for a number of years, and current thresholds do not take this type of damage into account. Peanut produces a lot of blooms, and not all of them will result in harvestable pods even in perfect conditions. The impact of caterpillar feeding on blooms is not known. I think it is reasonable to be more aggressive in making treatment decisions when significant bloom feeding is observed. What is “significant bloom feeding”?  That is a question that will have to be answered on a case by case basis taking into account the condition of the field, number of caterpillars, maturity of the crop, and personal experience

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2017 Stored Grain Protectants

For the first time in many years, we have many new products on the market. Here is an update from UGA Extension Entomologist Dr. Mike Toews and Auburn Entomologist Dr. Kathy Flanders:

Products for Empty Bins

  • Centynal EC – This is a good product for treating empty bins and elevator boots. Note that the active ingredient in Centynal EC, Defense SC and Suspend SC are identical so these are not good rotation partners.
  • Defense SC (labeled for empty bin use only) – This is a good product for treating empty bins and elevator boots, but is not labeled for application directly to grain. Note that the active ingredient in Centynal EC, Defense SC and Suspend SC are identical so these are not good rotation partners.
  • Suspend SC – This is a good product for treating empty bins and elevator boots. Note that the active ingredient in Centynal EC, Defense SC and Suspend SC are identical so these are not good rotation partners.
  • Tempo SC (labeled for empty bin use only) – Tempo is a good product for treating empty bins and elevator boots, but is not labeled for application directly to grain.

 Products for Application to Grain

  • Actellic 5E (labeled for corn only) – This product has been the standard for many years, but it is expensive. A full rate will provide protection from weevils for 9-12 months. Reducing the rate will decrease the longevity of the protection. Our data suggest that Actellic is susceptible to heat degradation in the drier when grain temperatures exceed 120 F.
  • Centynal EC (labeled for corn and wheat) – Centynal EC is a new formulation that will provide 3 to 6 months of protection from weevils at the 0.5 ppm rate or 6 to 12 months of protection at the 1.0 ppm rate. This material is heat stable in the drier (tested up to 150 F).
  • Diacon (labeled for corn and wheat) – Diacon is an insect growth regulator that is effective for killing nearly all immature grain moths and beetles, except weevils. The 4 oz per 1000 bu rate is sufficient for tank mixing.
  • Diacon IGR PLUS (labeled for corn and wheat) – This product is a premix of Centynal EC and Diacon. See comments above for rates and activity.
  • Malathion (labeled for wheat and corn) – Although widely used in the past, this product is no longer recommended due to well documented resistance in many stored grain insect populations.
  • Sensat (labeled for corn and wheat) – This product is new to the market, but has been in our evaluation program for several years. Test results show excellent weevil control for up to 12 months. No dryer stability data at this time.
  • Storcide II (labeled for wheat only) – Storcide II is an industry standard for stored wheat, but is not labeled for use on corn. Protection will degrade with heat and time.
  • Suspend SC (labeled for corn and wheat) – This product is an older formulation that must be completely suspended before measuring and requires frequent agitation. It provides 3 to 6 months of protection from weevils.
  • Three-way tankmix (only tested on corn) – UGA tests from 2014-2016 showed that a threeway tank mix of Centynal (8.5 oz) plus Diacon IGR (4 oz) plus PBO-8 Synergist (13.5 oz) will provide 6-9 months of protection from weevils. This is a moderately priced option for growers in markets where other products are unavailable or cost is a limiting factor.

Regardless of the product used, be mindful that grain protectants are not a silver bullet. Shelled corn should be dried to a maximum of 15% moisture content before dropping it in the bin.

Chemical applications should only be made to clean grain that will be stored for more than 3 months. Apply protectants at the bottom of the auger in a course spray to maximize coverage as the kernels are moving up to the top of the bin. Long-term grain storage requires appropriate moisture content, proper housekeeping, use of a spreader when filling bins, and managed aeration.

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Scout Cotton For Corn Earworms

UGA Entomologists Dr. Phillip Roberts and Dr. Mike Toews put this information together on corn earworms in cotton.

During the past week we have received a few reports of escaped corn earworm CEW) larvae in Bt cottons which exceed recommended thresholds. Bt cottons are not immune to CEW and never have been. All Bt cottons should be scouted for CEW and growers should be prepared to react in a timely manner if thresholds are exceeded. We have planted Bt cottons for over 20 years.  The technology has moved from a single Bt gene to two gene and now three Bt genes. The addition of Bt genes was for two reasons primarily; 1) to improve efficacy and increase the spectrum of activity and 2) for resistance management. The slide below is a general rating for Bt cottons for various caterpillar pests.

Activity on CEW varies by technology, however all technologies should be scouted. Entomologists in Georgia and other areas of the cotton belt believe we are seeing changes in the susceptibility of CEW to some Bt genes. We have been fortunate in Georgia in that only a small percentage of Bt cottons have required treatment for escaped CEW in recent years. However we have observed changes in performance of Bt corn in recent years, i.e. seeing more damage to corn ears. We are also seeing more feeding on squares in Bt cotton which was very rare 5 years ago. One aspect of Bt cotton that we must not forget is that all Bt cottons continue to provide excellent control of tobacco budworm.

When scouting Bt for CEW cotton scouts should examine the top 12 inches of the plant for eggs and larvae and also examine one bloom, one bloom tagged boll (be sure to look under bloom tag), and an additional boll lower in the canopy. If any damage is observed on the plant the entire plant should be searched. It is important to size larvae as small (< ¼ inch) or large (> ¼ inch). Once larvae reach ¼ inch in length it is likely those larvae will survive on the Bt plant and continue to feed. When we observe escaped CEW larvae they are often associated with fruiting structures near the uppermost white bloom.  So make sure you check blooms, bloom tagged bolls, and small bolls closely. The slide below shows various images of CEW in cotton.

The threshold for CEW larvae in Bt cotton is when 8 larvae ¼ inch or greater in length are found per 100 plants. When treating escaped CEW in Bt cotton coverage and penetration of the canopy with sprays will be important.  We must get the insecticide to the target as larvae will likely be down in the plant canopy. Control of larvae in bolls and under bloom tags will be difficult.

Pyrethroids have been the standard treatment for CEW for many years.  In parts of the cotton belt pyrethroid activity on CEW has deteriorated. For example some states in the Mid-South do not recommend pyrethroids for control of CEW due to pyrethroid resistance and field control failures. We annually monitor CEW susceptibility to pyrethroids in Georgia using adult vial tests. Basically we capture adult CEW moths in pheromone traps and place those in pyrethroid treated vials and monitor survival. During recent years and especially during 2016 we observed increased survival of CEW in these tests which suggests susceptibility is changing. However, we have not observed or been made aware of any field control issues when pyrethroids have been used for CEW control. With that said, we have made few field applications of pyrethroids for control of CEW in any crop during recent years. Bottom line is it will be important for us to check behind pyrethroid applications targeting CEW. There are non-pyrethroid alternatives that will provide very good control of CEW.  The slide below illustrates CEW survival in pyrethroid treated vials.

 

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Pecan Fruit Thinning

If you have over 60% of the terminals bearing fruit, the trees will benefit from thinning. This will improve quality this year and generate a better return crop next year. UGA Extension Horticulturalist Dr. Lenny Wells says early to mid-October harvest varieties should be about ready for thinning next week. Most of our varieties should respond when thinning next week and at least the first half of the following week. Sumner possibly even a little later. To know exactly when to thin you will have to slice nuts open and look at the development of the ovule inside the nut

When do you thin?

In most years, there is a window of only 10 – 14 days in which fruit thinning can be done successfully. Research has shown that… nuts should be removed when the ovule (cavity inside nut in photo below) is 50% to 100% expanded, but before the kernel enters the dough stage. Thus, the calendar date for fruit thinning of pecan will vary with cultivar and location, as well as from year to year.

After the female flower has been pollinated and fertilized, the ovule (the tissue that becomes the kernel) begins to expand and lengthen from the tip of the nut toward the stem. As the ovule expands, the space inside is filled with a watery substance called liquid endosperm. After the ovule extends to the stem end of the nut, and the nut reaches full size, the shell begins to harden from the tip backward. When the ovule is completely expanded, the kernel begins to fill and nuts pass from the water stage to the gel stage, to the dough stage.

Ovule (cavity) on the right is 70-80% expanded where left cavity is just starting.

To observe of nut development, slice through the nut to expose the ovule. When the nut is removed from the tree, an oval shaped scar is left on the shuck. Cut the nut lengthwise at a right angle along the long axis of the oval scar. A straight, lengthwise cut exposes the expanding ovule and liquid endosperm within the nut. Thinning should occur when the ovule or kernel has extended to half the distance toward the stem end of the nut. The larger the nut size, the earlier in the ovule expansion period thinning can take place, because larger nuts are easier to shake off the tree

How much to remove?

The amount of nuts to remove varies with nut size, cultivar, crop load, and environmental factors. Judging the tree’s crop load is another important factor in the decision to thin. This is a practice that takes experience. The percentage of nut-bearing terminals can be developed by observing the number of fruiting terminals counted from an observation of 50-100 random terminals on a tree.

Trees with almost 100% of the shoots bearing fruit and a cluster size greater than three are overloaded and should benefit from thinning. Optimum crop load varies with cultivar and may range from 50-70% fruiting shoots. Varieties with small nut size can be thinned more lightly than those with large nut size. For example, optimum crop load on cultivars greater than 70 nuts per pound may be 60-70% fruiting shoots. Nuts in the size range of 50-70 nuts per pound, like Cape Fear or Stuart, have an optimum crop load of 50-60% fruiting shoots. While varieties with large nut size of less than 50 nuts per lb may have an optimum crop load of only 45-50% fruiting shoots.

Additional Tips

The major mistake growers make when first time attempting to fruit thin is not removing enough nuts. When shaking begins, don’t be alarmed by the number of nuts that fall. Trees should be shaken two to three seconds at a time, evaluated, and then shaken again if needed. This process should be repeated until the operator has a feel for how hard to shake to achieve the desired results.

Increased profit potential through enhanced size, quality, and return crop has so far been shown with mechanical fruit thinning on Cape Fear, Creek, Pawnee, Schley, Stuart, Sumner, Kiowa, Cheyenne, Shoshoni, and Mohawk. This does not mean that the practice is not profitable on other cultivars, but simply that it has not been adequately tested for those cultivars not mentioned. It is likely that most pecans with fruiting characteristics similar to those previously mentioned would respond favorably.

 

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